What Is the Function of Testosterone (TST)?

By BSc, MSc (embryologist) and BA, MA (fertility counselor).
Last Update: 11/10/2014

Testosterone is a male hormone that takes part in the development of the male gonads and the apparition of the secondary male sex characteristics. It’s produced mainly in the testicles. However, a small amount is also released by the suprarenal glands. It’s an anabolic steroid and it’s the main male sexual hormone.

Even though it’s true that testosterone is the main androgenic hormone, not only men produce it. Women also produce testosterone but of course, a lower quantity. In women, it’s produced by the ovaries and the suprarenal glands and it’s linked to the increase in female sexual desire.

The different sections of this article have been assembled into the following table of contents.


In men this hormone is vital for the proper development of the male reproductive system and the secondary sex characteristics, such as apparition of beard, hair in the body, a deep voice, increased muscle mass and heavier bone structure. It’s also beneficial for the bones proper formation, since it prevents osteoporosis.

This hormone has two different effects: on the one hand, it produces an androgenic effect, helping the formation of male sex characteristics and its permanence during life; on the other hand it has an anabolic effect increasing the bone structure and strength, apart from stimulating growth and bone maturation.

The effects of testosterone on the male gonads are:

  • Stimulating spermatogenesis in the seminiferous tubules.
  • Stimulating sperm maturation.
  • Helps the growth of the penis, scrotum and endocrine glands.
  • Increasing the growth of the testes.
  • Stimulating the sperm formation.
  • Stimulating the development of hair.
  • Increasing libido and sexual desire.

Therapy with testosterone

Therapies with testosterone

An analysis is carried out to check the quantity of testosterone in blood plasma. In an adult man the quantity is usually 20 times higher than in an adult woman. The normal values are 300 - 1,000 ng/dL for men and 15 – 70 ng/dL for women.

The lack of testosterone in men can provoke difficulties to maintain erections, lack of sexual desire, low seminal parameters and decrease in strength and body size. If several analysis are carried out and the results reveal that the levels of testosterone are low and the symptoms are only due to this cause, a hormonal therapy with testosterone can be applied.

The administration method of testosterone will vary depending on the characteristics of men and the shortage that he has. The method can be: injections, gel, patches, or implants. The artificial administration of testosterone can have secondary effects, that’s why medical check-ups and a control of the doses are of vital importance. The adverse effects are: size increase of the breasts, fluid retentions or size increase of the prostate. The last one is the most dangerous one, so doctors usually carry out a specific examination of the prostate to make sure that there are no tumors on the area, decreasing the possibilities that cancer is developed after the abnormal prostate size increase.

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Authors and contributors

 Cristina Mestre Ferrer
Cristina Mestre Ferrer
BSc, MSc
Bachelor's Degree in Biological Sciences, Genetics & Human Reproduction from the University of Valencia (UV). Master's Degree in Biotechnology of Human Assisted Reproduction from the UV and the Valencian Infertility Institute (IVI). Embryologist at IVI Barcelona. More information about Cristina Mestre Ferrer
Adapted into english by:
 Sandra Fernández
Sandra Fernández
Fertility Counselor
Bachelor of Arts in Translation and Interpreting (English, Spanish, Catalan, German) from the University of Valencia (UV) and Heriot-Watt University, Riccarton Campus (Edinburgh, UK). Postgraduate Course in Legal Translation from the University of Valencia. Specialist in Medical Translation, with several years of experience in the field of Assisted Reproduction. More information about Sandra Fernández

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